1. Technical Field
The present invention relates to the field of turbine blades, and, in particular to shrouded turbine blades separated by a shroud damper.
2. Background Information
Turbine sections within axial flow turbine engines or turbo pumps (e.g., fuel or oxygen) include a rotor assembly comprising a rotating disk and a plurality of rotor blades circumferentially disposed around the disk. Each rotor blade includes a root, an airfoil, and a platform positioned in a transition area between the root and the airfoil. The roots of the blades are received in complementary shaped recesses within the disk. The platforms of the blades extend laterally outward and collectively form a flow path for fluid passing through the rotor stage.
In addition to a root, an airfoil and a platform, the blade may also include an integral tip shroud. The tip shroud generally seals a leakage path at the outer diameter, provides stiffness for the tip section to allow tuning against critical vibratory modes and provides damping at the contact interface of adjacent shroud surfaces. Contact forces required to achieve damping are generally developed due to blade untwist under centrifugal forces. However, in the case of high energy turbopumps, the airfoils are relatively short (e.g., about 2 inches/5.1 cm) and have negligible twist along the span thus preventing the airfoil from developing the conventional contact forces along the shrouds. In addition, the negligible twist prevents the shroud from sealing the leakage path.
There is a need for a damper and/or sealing structure between adjacent turbine tip shrouds.